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I have read that the vision pro 8321 is a 3 stage t-stat
however there seems to be the opinion that it can't be used on 1 stage
heat pump w/2 stage fossil back-up.
I like the technology of the VP does anyone make a similar
device that can be used in the setup I have.
Also I read the manual for Vision pro and
under the instructions for testing it it says under under installer test #3 option 2 both the stage 1 and 2 turn on. Can doing this damage the heat pump? I didn't think you should run
the gas heat with the heat pump running.

True, don't run the heat pump with the furnace fired. You can use that Vision Pro to run the set up you describe using a outdoor tstat with single pole double throw contacts. The wiring isn't that hard to figure out.

Originally posted by subdewd Also I read the manual for Vision pro and
under the instructions for testing it it says under under installer test #3 option 2 both the stage 1 and 2 turn on. Can doing this damage the heat pump? I didn't think you should run
the gas heat with the heat pump running.

That test would be for a 2 stage heat pump. If you set the stat up so it controls the fossile fuel back up, it won't ever let the heat pump and furnace run at the same time.

OK. You would think the firmware would keep that test
from being available with Single stage chosen as option
during setup. Is the white rogers 3 stage a better choice?
Or does that need to be rigged up like you said with outdoor
tstat? Can you recommend a outdoor Tstat or are they pretty
much the same?

OK so can you say how it, namely the VP would be used with a 2 stage fossil back up? They have aux and emergency terms.
Y is first srage (HP), second is Aux? or is it put Y2 on
first stage of the gas backup and aux on the stage 2 gas.
Does adding the sensor lockout the compressor whan gas is called . I noticed on the White roger 371 it stated that
the compressor will run with aux(gas) on for up to one minute.

At 50 and above VP will run HP only. ( outside air temp)35 to 50 HP and back up. Below 35 Back up only. That works with Elec back up but not gas or oil. I wire a relay into the furnace so it cant run when comp is on.

yeah that'll work, Run the call for stage 1 HP through NC
contracts. Have the call stage 2 through coil and NO contacts to W1 on furnace. Call stage three straight to W2 on furnace. You would think Honeywell would build a solution into their box.

That figures jultzya, so how about stage three? which is gas stage 2. So far the closest thing I can see is just set the VP to 2 stage and let the furnace time from low to high output.The Vp instructions for 3 stage show 1 and 2
for the HP and 3 for fossil back up, which I suppose is more common. By the way thanks everyone for your response it just shows how different approachs to the same problem
leads to different solutions. I called Honeywell last week and the guy I tolked to gave some advice but I could tell from how quick he answered that he was following a scipt.